Enter the flow rate, cross-sectional area of the orifice, acceleration due to gravity, and the height of the fluid above the centerline of the orifice into the calculator to determine the orifice coefficient.

Orifice Coefficient Formula

The following formula is used to calculate the orifice coefficient.

Cd = Q / (A * √(2*g*H))

Variables:

  • Cd is the orifice coefficient (dimensionless)
  • Q is the flow rate (m³/s)
  • A is the cross-sectional area of the orifice (m²)
  • g is the acceleration due to gravity (m/s²)
  • H is the height of the fluid above the centerline of the orifice (m)

To calculate the orifice coefficient, divide the flow rate by the product of the cross-sectional area of the orifice and the square root of twice the acceleration due to gravity multiplied by the height of the fluid above the centerline of the orifice.

What is an Orifice Coefficient?

The orifice coefficient, also known as the discharge coefficient, is a dimensionless number used in fluid dynamics to model the flow rate of fluids through an orifice, nozzle, or valve. It accounts for the effects of viscosity, turbulence, and other factors that can affect the flow rate. The coefficient is typically determined experimentally and can vary depending on the Reynolds number, the shape of the orifice, and the roughness of the surfaces. It is used in the calculation of the flow rate to provide a more accurate prediction.

How to Calculate Orifice Coefficient?

The following steps outline how to calculate the Orifice Coefficient.


  1. First, determine the flow rate (Q) in m³/s.
  2. Next, determine the cross-sectional area of the orifice (A) in m².
  3. Next, determine the acceleration due to gravity (g) in m/s².
  4. Next, determine the height of the fluid above the centerline of the orifice (H) in m.
  5. Next, gather the formula from above: Cd = Q / (A * √(2*g*H)).
  6. Finally, calculate the Orifice Coefficient (Cd).
  7. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

flow rate (Q) = 0.5 m³/s

cross-sectional area of the orifice (A) = 0.1 m²

acceleration due to gravity (g) = 9.8 m/s²

height of the fluid above the centerline of the orifice (H) = 2 m